Enabled/disabled predicate encryption in clouds

Predicate encryption is a cryptographic primitive that provides fine-grained control over access to encrypted data. It is often used for encrypted data search in a cloud storage environment. In this paper, we propose an enabled/disabled predicate encryption scheme, which is the first work that provides timed-release services and data self-destruction (they correspond to the terms “enabled” and “disabled,” respectively). Owing to these properties, the sender can set the readable/unreadable time of the files to be sent to the receiver. The receiver can read the sent file only after the readable time. After the unreadable time, the structure of the file will be destroyed and the file will become unreadable. Furthermore, for practical usage purposes, the extended scheme, which is based on the proposed scheme, provides not only timed-release services and data self-destruction but also long message encryption and undecryptable search. In the extended scheme, the length of encrypted messages does not depend on the order of the group. Moreover, the cloud server can obtain only the matched ciphertexts after the search.     

A time-aware searchable encryption scheme for EHRs

Despite the benefits of EHRs (Electronic Health Records), there is a growing concern over the risks of privacy exposure associated with the technologies of EHR storing and transmission. To deal with this problem, a time-aware searchable encryption with designated server is proposed in this paper. It is based on Boneh's public key encryption with keyword search and Rivest's timed-release cryptology. Our construction has three features: the user cannot issue a keyword search query successfully unless the search falls into the specific time range; only the authorized user can generate a valid trapdoor; only the designated server can execute the search. Applying our scheme in a multi-user environment, the number of the keyword ciphertexts would not increase linearly with the number of the authorized users. The security and performance analysis shows that our proposed scheme is securer and more efficient than the existing similar schemes.